Adjustable reamer



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Oct. 3, 1944. w,l BROGAl ET AL 2,359,296

E ADJUSTABLE BEAMER A Filed July 4, 1942 IIHI ,Fi EL 5 Wilson C Brnga Wilbur'A .'chaich Patented Oct. 3, 1944 ADJUSTABLE BEAMER Wilson C.

Broga, Westfield, and Wilbur A. Schaich, Springfield, Mass.

Application July 4, 1942, Serial No. 449,819

(Cl. 'T7- 75) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Goverment for governmental purposes Without the payment to us of any royalty thereon.

This invention relates to an adjustable reamer and particularly to an improvement in the construction shown in a co-pending application, Serial No. 449,809, filed July 4, 1942i, in the name of Wilson C, Broga, who is a joint inventor of this application.

The reamer construction described in the above mentioned application permits the grinding of the blades of an adjustable reamer for sharpening purposes by a rotating wheel grinder having its axis parallel to the axis of a reamer and eliminates the necessity of removal of the blades from the reamer for grinding purposes. With this construction, which will be more fully described, it is still necessary to shift the axis of the grinding wheel with respect to the axis of the reamer in order to grind a slight longitudinal taper on the work entering end of the lreamer blades to eliminate excessive Wear on such end which would occur if such taper were not provided. This recentering operation consumes a substantial amount of time, unless a complex and expensive grinderis utilized.

It is accordingly an object of this .invention to produce an improved adjustable reamer which may be reground in much less time than previously possible.

A particular object of this invention is to produce an adjustable reamer and grinding method wherein al1 necessary grinding of the reamer surfaces may be accomplished by radial grinding, i. e., with the axis of the grinding wheel parallel to the axis of the reamer and without the necessity of changing the axis of the Vwheel with respect to the reamer.

The specic nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in Which- Fig. 1 is a side elevational view of an adjustable reamer shown partly in longitudinal section with the cutter :blades shown in working position.

Fig. 2 is a cross-sectional view taken along the plane 2-2 of Fig. 1.

Fig. 3 is a side elevational view shown partly in longitudinal section with the cutting .blades in position for grinding a slight axial taper on the work entering ends of the cutting blades.

Fig. 4 is a right end elevational View of the reamer shown in Fig. 1. V

Fig. 5 is a cross sectional view taken along the plane 5 5 of Fig. l.

As shown in assembled relation in Fig. 1, the reamer comprises a shank I, one end Ia of which maybe engaged by the tool holder of any suitable operating mechanism (not shown). 'I'he remaining portion of the shank is provided With external threads Ib. Longitudinal slots Ic are provided in the shank I. The number of these slots depends on the number of reamer blades which it is desired to utilize. In this preferred embodiment of the invention, the reamer is shown as having four blades and accordingly four slots Ic are provided. The slots Ic are disposed in the shank I in such a manner that their depth axes are angularly disposed with respect to the radii of the shank, or, stated otherwise, their depth axes are offset with respect to the center of the shank, as best shown in Figs- 2 -and 5. The slots Ic extend throughout thelength of the threaded portion Ib of the shank I.

The depth of the slots Ic varies along the axis of the reamer shank I. Beginning at the rear end of the threaded portion of the shank I, or the left hand end as shown in Figs. 1 and 3,l the slots increase indepth uniformly along the axis of the shank until a point is reached aboutthe distance of half the length of a reamer blade from the end of the shank. The location of this point, shown at 1, may be varied depending on the range of the longitudinal tapers which it may l be desired to grind upon the reamer blades as will be explained in rmore detail later.` From this point 'I to the end of the threaded portion of the shank I, the depth of the slots is either constant or decreases uniformly. This construction is in distinct contrast to the slot construction described in the above mentioned co-pending application wherein the depth of the slots increases uniformly throughout their length. To facilitate machining, the bottom of the slots Ic inthe region of the point 'I may comprise an arcuate surface,

, A reamer blade 2 is tted snugly into each' of the slots Ic but the t is sufficiently loose to permit the blades to be freely moved throughout the slots. The blades 2 are securely held in any desired position Within their respective slots by means of nut members 3 and 4 which are screwed upon the shank threads I b on each side of the blades 2. The nut members 3 and 4 each have an overhanging axial extension 5 and 6 respectively on their sides adjacent the blades 2. The surfaces of contact between the blades 2 and the nut extensions and 6 are inclined as respectively shown at 5a and 6a. Accordingly the blades 2 will be securely held within the slots Ic regardless of whether they are located in the shallow' in Fig. 2, the external surfaces 2a of the blades 2 l acquire a curvature having a radius equivalent to the distance from the surfaces 2a to the center of the shank l. It is necessary of course to rotate or rock the reamer about the centers Id and le during the grinding operation.

To use the reamer on a work piece the nuts 3 land 4 are loosened, the blades 2 moved to the left, as Viewed in Fig. 1, from the grinding position and of course secured in the new position by tightening of the nuts 3 and 4. In such position, shown in cross-section in Fig. 2, the cutting radius of the leading edges 2b of the surfaces 2a now is a larger radius than the radius to which the surfaces 2a were ground in the grinding position. This increase in radius of the leading edge 2d is of course produced by the radially outward movement of the blades 2 caused by the tapered depth of the slots lc. Hence in any position of the blades 2 to the left of the point 1 as viewed in Fig. 1, a relief angle will be obtained between the blade surfaces 2a and the work surface. The magnitude of such angle willv depend upon the slope of the slots lc and the distance the blades are moved in the slots to the left of the grinding position. It is apparent that if the radius of the work piece is known, the slope and length of the slots lc may be readily proportioned to produce any desired relief angle. Furthermore the initial working position of the reamer blades 2 may be selected to not only be to the left of point 1 but also be to the right of the beginning of the slots lc. With this condition,

greatly increased life of the reamer blades 2 may be obtained since after each successive grinding the blades may be moved slightly more to the left, to the beginning of the slots Ic, and thel increased cutting radius of the leading edge 2b thereby obtained will compensate for the decrease in height of the reamer blades due to the grinding.

For proper operation of the reamer, a slight axial taper should be provided on its work entering end in order to prevent concentration of wear upon the entering portion of the blade surface. Such a taper may be ground upon a reamer of the construction herein vdescribed without change in the centering of the reamer or of the grinding wheel.

The grinding of this taper is accomplished immediately afterthe initial grinding with the right edge of the blade near the point 1. The nuts 3 and 4 are loosened and the blades 2 are moved to the right, as viewed in Fig. 1, past the point 'I and thereby enter into that portion of the slots Ic wherein the depth is constant or decreases along the axis of the shank. The effect of this change in slot'l depth will be to project the front end; of the blades 2 radially outward, the amount depending upon the slope of the base of this portion of the slots Ic and the distance to which the reamer blades 2 enter such portion. The blades are then secured in this new position, as shown in Fig. 3, by tightening of the nuts 3 and 4 and reground without changing the centering of the reamer or the grinding wheel.

The effect of this grinding will be to establish a new surface indicated at IU in Fig. 3. Since the taper to be produced is relatively slight this grinding will not materially affect the curvature of the surfaces 2a. Hence when the blades 2 are moved back rin the slots lc to a working position to the left of the point 1, they will still have the desired angle of relief produced by the initial grinding and in addition will have a slight longitudinal taper on the forward end of the blades.

It should be understood that a reamer of the construction described can be readily designed for any substantial working diameter and that any desired relief angle or taper may be obtained by merely changing the length or rate of depth increase or decrease or the length of the slots l'c. Furthermore the methods described may be utilized to grind a taper on a conventional adjustable reamer having a constant slot depth by. providing a slight decrease in slot depth at theforward end of the slots.

It is apparent that if it is desired lto grind the blades with a taper extending the full length thereof then only one grinding operation isnecessary. In such case the blades would be initially ground with their forward ends projectingl forwardly past point 1.

We claim:

1. The method of, providing cutting.. relief and a taper on the movable blades of an expansible reamer comprising the adjustment of the-blades in suitable variable depth slotsl in a holder to a position where the cutting edgesare-located at a. smaller radial distance than the. desired Working radius, grinding said blades toa common cylind-rcal surfaceof radius smaller than the desired working radius, then adjusting said blades in said slots to a position where the work entering ends of the blades are radially displaced toa greater extent than the other ends, vgrinding at least the work entering end portions of the blades to a common cylindrical surface, then locating said blades in a working position in said slots where the maximum radii of the cutting edges of said blades equal the desired working radius and the bases of said blades are parallel to their position during the first grinding.

2. The method of simultaneously providing cutting relief and a taper on an expansible reamer having wedge-shaped blades comprising the'adjustment of the blades in suitable variable depth longitudinal slots in a holder to a position where the cutting edges are located at a smaller radial distance than the desired working radius, grinding said blades to a common cylindrical surface of radius smaller than the desired working radius, then locating said blades in a working4 position in said slots where the maximum radii of the cutting edges of said blades equal the desired working radius and the bases of said blades are inclined with respect to their lposition during the grinding at an angle equal to the desired angle of taper.

3. An adjustable reamer comprising a shank, a plurality of longitudinal slots equally disposed around the periphery of said shank, each of saidY slots comprising a forward work entering end' portion and a rear portion, the baseof said rear' slots and the slope of such portion to produce a l0 substantial radial displacement of said blades when moved from one end of the slots to the otheig whereby a desired relief clearance of the trailing edges of the .blades is obtained, and means for securing said [cutting blades in said slots in a plurality of positions along the length of the slots.

WILSON C. BROGA. WILBUR A. SCHAICH. 

